Many industries discharge high-strength organic wastewaters with low biodegradability. These effluents are difficult to treat because of containing toxic substances and of its high chemical stability. It poses a great risk to the environment and human health once these effluents enter into water body. Therefore, it has always been a difficult problem in wastewater treatment.
Anaerobic hydrolysis-acidification process as the first stage of anaerobic fermentation can reduce the macromolecules and non-biodegradable organics of the sewage to biodegradable micro-molecular organics, making them easier to be degraded in the following treatment. Compared to the whole-process anaerobic technology which must go through methanogenic stage, anaerobic hydrolysis-acidification is of short HRT, convenient operation and quick startup. Small molecule carboxylic acid formed in this stage is available for the utilization in the consequent anaerobic or aerobic process. Therefore, anaerobic hydrolysis-acidification is preferable and widely used in sewage treatment, especially in industrial wastewater treatment. In that case, the wastewater after anaerobic hydrolysis-acidification is directly discharged into aerobic treatment to avoid anaerobic methanogenesis because the later needs a long-term HRT and a strictly operational condition.